DESCRIPTION: This is a well-written application from an investigator with a long period of support. These investigations use human subjects and involve three experiments addressing four aims. The first aim is to assess the hypothesis that high energy intakes on high fat diets are due to the energy density of those foods rather than specifically relating to other properties of fat itself. In the second specific aim the hypothesis evaluated is that the weight of food acts through preabsorptive mechanisms while energy and nutrient content act through postabsorptive mechanisms. In the third specific aim the intent is to test the hypothesis that obese humans have an impaired ability to sense and respond to energy and fat content of foods within the short and long term periods. The fourth specific aim is to test whether it is true that foods of low energy intensity suppress initial hunger and prolong satiety more when they are matched to high density foods on a weight basis. The experiments testing these hypotheses involve two sets of short term feeding studies manipulating preloads, but significantly involving multiple sittings for the same individual subject. The third experiment is a long term comparison of diets of similar energy density but differing in fat content and then doing the reverse experiment of changing energy density while fixing fat content. The experiments carefully vary fat content while keeping the energy content constant or vice versa, all while maintaining constant palatability.